1. Field of the Invention
The present invention relates to a magnetic detecting element having a pinned magnetic layer whose magnetization direction is fixed in one direction and a free magnetic layer formed on the pinned magnetic layer with a nonmagnetic material layer interposed therebetween. More particularly, the present invention relates to a magnetic detecting element which can stabilize reproduction power.
2. Description of the Related Art
FIG. 8 is a partial cross-sectional view of a magnetic detecting element according to the related art (spin-valve type thin film element) taken along a direction parallel to an opposing surface to a recording medium.
In FIG. 8, reference numeral 1 denotes a base layer formed of Ta. On the base layer 1, a seed layer 2 formed of NiFeCr is formed.
A multilayer film T is formed by laminating an antiferromagnetic layer 3, a pinned magnetic layer 4, a nonmagnetic material layer 5, a free magnetic layer 6, and a protective layer 7 in that order on the seed layer 2.
The free magnetic layer 6 and the pinned magnetic layer 4 are formed of a Heusler alloy, such as Co2MnGe or the like. The nonmagnetic material layer 5 is formed of Cu, and the antiferromagnetic layer 3 is formed of PtMn. Further, the protective layer 7 is formed of Ta.
An exchange coupling magnetic field is generated at the interface between the antiferromagnetic layer 3 and the pinned magnetic layer 4, and the magnetization of the pinned magnetic layer 4 is fixed in a height direction (in FIG. 8, Y direction).
On both sides of the free magnetic layer 6, hard bias layers 8 are formed of hard magnetic material such as CoPt, and the top, bottom, and end portions of each of the hard bias layer 8 are insulated by an insulating layer 9. By a longitudinal bias magnetic field from the hard bias layers 8, the magnetization of the free magnetic layer 6 is aligned in a track width direction (in FIG. 8, X direction). On the top and bottom of the multilayer film T, electrode layers 10 and 10 are formed.
If an external magnetic field is applied to the magnetic detecting element shown in FIG. 8, the magnetization direction of the free magnetic layer 6 is relatively changed with respect to the magnetization direction of the pinned magnetic layer 4, and then a resistance value of the multilayer film is changed. When a sense current having a predetermined current value is flowing, by detecting the change in resistance value as a change in voltage, the external magnetic field is detected.
The magnetic detecting element having the pinned magnetic layer formed of the Heusler alloy is described in JP-A-2003-309305 (page 8 and FIG. 4).
FIG. 9 is a partial schematic view showing the magnetic detecting element shown in FIG. 8 on a magnified scale. It is difficult to make the surface of the pinned magnetic layer 4 a completely planarized surface, and normally, fine waviness occurs at the surface. If waviness occurs at the surface of the pinned magnetic layer 4, similar waviness also occurs at the surfaces of the nonmagnetic material layer 5 and the free magnetic layer 6.
FIG. 9 is a schematic view showing sections of the pinned magnetic layer 4, the nonmagnetic material layer 5, and the free magnetic layer 6 taken along the Y direction. If such waviness occurs, as shown in FIG. 9, magnetic poles occur at the wavy portion of the surface of the pinned magnetic layer 4. The magnetic poles also occur at the wavy portion of the free magnetic layer 6 facing the pinned magnetic layer 4 with the nonmagnetic material layer 5 interposed therebetween. Accordingly, a ferromagnetic coupling magnetic field Hin caused by magnetostatic coupling (topological coupling) between the pinned magnetic layer 4 and the free magnetic layer 6 becomes stronger. Therefore, the free magnetic layer 6, which should be magnetized in an X direction of FIG. 9, is magnetized in a Y direction of FIG. 9. As a result, there is a problem in that asymmetry of reproduction waveforms when an external magnetic field whose direction is shifted by 180 degrees is applied is increased.